You wouldn't be able to connect high speed components like graphics cards and NVMe drives to your computer
without the PCI Express bus that's been a fixed on our motherboards
for over a decade now. If you're not familiar, you can connect your devices via PCI Express
in a few ways. Most commonly, you insert an adapter card
into one of these slots right here or an M.2 SSD right over here.
But did you know that not all PCI Express connections
are the same? You see PCI Express can connect your devices
either directly to your CPU or to the chip set which sits between your CPU
and some of your other components like your Ethernet jack or some USB ports.
This might be a point of confusion if you've seen a motherboard that supports say
40 PCI Express lanes, but the CPU can only run one graphics card
at 16X speed or two cards at 8X speed each.
I mean, shouldn't all of those PCI Express lanes let you plug in more than just one or two adapter cards?
This is where the difference between chip set versus CPU PCI Express lanes comes into play.
Most consumer CPUs will have 16 or 20 lanes
running directly off of them, which you should be using for your graphics card
for the best performance. But then why is that better than using the lanes
that come off the chip set? Well, one reason is that having the extra step
of routing data through that chip set introduces latency
which can slow down your performance. Perhaps a bigger reason though
is the link that connects the chip set back to the CPU.
You see, although you'll often see diagrams showing that 16 or 20 or even more PCI Express lanes
come off of the chip set, the connection that it has to the CPU
is actually quite narrow. It might be only four lanes wide.
Now chip sets provide lots of lanes to other components and peripherals
because of how many things connect to it. Firmware, SATA, audio, Ethernet, USB devices,
but these are all either relatively low bandwidth
applications or they're very unlikely
to all be fully utilized at the same time. So having them bottlenecked as they send data to the CPU
isn't all that big of a deal. That limited bandwidth can hurt you though
if you try to connect something that moves considerably more data such as a graphics card
while you're also trying to use all that other stuff.
Now the long 16X PCI Express slots on your motherboard,
those are typically connected directly to the CPU.
So you don't have to worry too much about accidentally connecting a graphics card
to your chip set. But because those usually too share the same 16 lanes,
you can't run two cards in them at full speed unless you have a higher end CPU that supports more lanes.
Additionally, if you have a standard 16 lane Intel CPU,
this means that an NVMe drive installed in an M.2 slot on your board
is going to be routed through the chip set. Now you shouldn't see a ton of performance loss,
but the aforementioned latency plus any heavy network SATA
or USB traffic being routed through those four lanes back to the CPU could result in some slowdowns
depending on your workload. On a related note, this is actually why some SATA ports
get disabled when you plug in an M.2 drive since those ports are also connected to the chip set
and they share bandwidth. The good news though is that if you're trying to squeeze
every ounce of performance out of a drive, Intel's upcoming 11th gen desktop CPUs
are supposed to have 20 lanes coming directly off the CPU,
four of which are meant to support an M.2 drive.
And if you're on a Ryzen platform, you're in luck because you already have 20 or more lanes coming off the CPU.
It's kind of like chip manufacturers widening the highway for us,
but without the punitive speed limits. Thanks for watching guys, like, dislike,
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